Most well-trained mechanics loathe to hear these words: “I already got the part.” That’s because, more often than not, the well-intentioned driver trying to save a few bucks has guaranteed a future breakdown or another repair job by a mechanic who’s probably biting their tongue to prevent “I told you so” from escaping their lips.

You can tell fairly early on in the TikTok by Phoenix-area mobile mechanic Tim Fountas (@timotheosfountas) that he’s taken more calls than he’d like from potential customers who have turned to Amazon or eBay for parts, rather than letting him source them from his preferred suppliers.

He begins by describing an interaction with a customer who calls to say they have the part, but not the tools to do the work.

“I know a rental place. It’s called Harbor Freight,” he says sarcastically in the clip that’s been viewed more than 2,500 times. “You can buy a socket set, and then when you’re done with it, just return it. Then you don’t have to call me. You can save some more money.”

In another case, a customer opted for the cheapest brake components available, only to find the steering wheel shaking under normal braking shortly after. “The rotors were warped pretty bad,” he said.

Those kinds of callbacks aren’t rare. Early in his career, when he was more willing to take on jobs using customer-supplied parts, Fountas found himself retracing his steps more often than he’d like.

“Out of 10 instances, I would say a good 60%… I had to go back,” he said.

How Do Mechanics Feel About Customers Providing Parts?

A scroll through the comments on the video shows that most mechanics feel pretty much the same as Fountas about customers who provide their own parts.

Some draw a hard line. “We don’t install customer parts!!!” noted one.

Others point to the same cycle Fountas described, where a failed fix quickly becomes the technician’s problem.

“No warranty. Half the time the part is wrong,” one commenter wrote, adding that customers often return expecting labor refunds when the repair doesn’t hold.

Fountas said he’ll occasionally make exceptions, but only under specific conditions. Parts sourced directly through a dealership, for example, lend more confidence in both quality and compatibility. The bargain-bin alternatives that show up in a lot of these calls don’t inspire the same confidence, however.

For the people making those calls, though, the logic is straightforward. They’ve already spent the money, tracked down what they believe is the right part, and just need someone to install it. From their perspective, the fix is already halfway done.

That’s where the disconnect lies. What looks like a simple install from the outside often skips the steps that actually determine whether it’s the right part—or even the right repair.

That leaves mechanics in a position where the line between labor and responsibility isn’t always clear. Install the part, and you risk being tied to whatever happens next. Turn the job down, and the customer moves on to an unscrupulous mechanic or technician who might take it without feeling any guilt.

For Fountas, that’s why the Harbor Freight suggestion keeps coming up. In his mind, if the goal is to save money and skip the diagnostic process, he figures the most straightforward path is for the overzealous customer to see it through all the way themselves.

Fountas said the customers he hears from in these situations are usually focused on getting back on the road as quickly and cheaply as possible. But without confirming the root cause of the issue, even a correctly installed component can leave the original problem unresolved, or create new ones.

“I always try to talk them out of it,” he said. “Unless it’s a dealership part, I won’t do the install.”

Even then, he added, most people aren’t looking for a second opinion by the time they pick up the phone. They’re looking for someone willing to follow instructions, rather than an expert whose professional opinion might run counter to their own.

Fountas estimates, “90%of the time, they got their mind made up.”